The present invention relates to unloader valves, and particularly to unloader valves used with positive displacement pumps. More particularly, the present invention relates to a flow-actuated unloader valve for a pressure washer system.
Pressure washers provide a supply of high-pressure fluid for performing various tasks (e.g., paint and stain removal, drain cleaning, driveway cleaning, etc.). Usually the water is mixed with a cleaning solution such as soap, ammonia solution, bleach, or other chemicals.
Pressure washers often include an engine that drives a high-pressure pump to supply the cleaning fluid. A trigger-actuated valve (i.e., spray gun) mounted to the discharge hose from the pump allows the user to remotely control the supply of high-pressure fluid. When the trigger is depressed, cleaning solution is discharged. When the trigger is released, the flow of fluid stops and the pump is disengaged, the engine is turned off, or the high-pressure fluid is bypassed to avoid causing damage to the pressure washer system. To that end, many pressure washers include unloader valves that bypass fluid back to the fluid reservoir when the fluid is not being discharged.
Unloader valves, sometimes referred to as “bypass valves” or “diverter valves”, are used as a control mechanism for pressure washer systems. The unloader valve controls the pressure and the direction of flow within the system. Located between the outlet side of a pump and a discharge device (such as a spray gun), the unloader valve diverts fluid from the pump outlet back to the pump inlet through a bypass passage when the discharge passage becomes blocked (spray gun valve closed), thereby reducing pressure within the pump. When the discharge passage is unobstructed (spray gun valve open), the unloader valve redirects fluid back to the discharge device and allows the pump pressure to rise back to its' normal operating pressure.
Some pressure washer systems include the ability to inject cleaning solution directly into the discharge stream exiting the high-pressure side of the pump. To add cleaning solution, the user premixes the solution with the water or the solution is drawn into the pressure stream by vacuum with the use of a venturi, this method is commonly referred to as “chemical injection”. Chemical injection typically requires a separate apparatus adding cost and complexity to the pressure washer. Of the known pressure washer systems to have “chemical injection”, all require the use of additional components to perform this task. Such additional components may include a separate venturi, housings, o-rings, etc.